The only real plot hole I’d argue would be the keys. This explains the plot really well. What we saw was one pattern of events, there’s a separate pattern of “Even Jess” events which result in Even Jess-1 (the one our Jess refuses to shoot) hacking Even Jess-3 to death. This means the events are always an infinite loop where everyone dies. The Odd-Jess we followed the pattern of will end-up becoming Even-Jess3 in every loop.

This means the pattern goes:

Odd Jess1 (the beginning of the film where she comments she remembers the place), Odd Jess2 (where she refuses to shoot and witnesses Even-Jess1 kill Even-Jess3), Odd-Jess3 where she becomes the killer despite previously refusing to kill Even-Jess1 who is Even-Jess2 at that point (staying out of sight and seeing Odd-Jess3 becoming a killer), and then Odd-Jess3 being tossed off by Odd-Jess1. When she returns, she’ll be Even-Jess1 and then killed as Even-Jess3. Therefore, everyone in the ship dies infinitely, including Jess. So, there’s not actually an infinite loop in the strictest sense for Jess, since Jess will kill her Even-Jess3 self eventually, but the pattern itself will go on infinitely.

Jess will never save Tommy and accidentally ends-up killing him in the car crash and then cheating the Taxi Driver (who either represents Charon or Death) and goes back on the boat to kill alternate self and then be killed by her alternate self. If she is only stuck in an Even-Jess loop, then it would be a severe plot hole and the story would lose coherence that way.

Insofar as everything else in this groundhog-day style murder-mystery and horror film . .  . I think the tension and shock was done incredibly well. The scene with Sally and her many dead bodies was very vivid, memorable, and disturbing. The acting was very well done and I didn’t find the characters to be all that stupid, but one could argue Jess-3 not telling the others what is going on and choosing to just kill them is a plot hole in and of itself. But, it sort of makes sense, due to her desperation to get to the boat that loops back every time and she’s obviously not thinking clearly due to being traumatized by the repeated freak occurrences.

As far as ratings . . . I’m not entirely sure, but I suppose a 4 / 5 stars.